Uh, isn't this the sort of thing that's been going on since......since.....since, oh, about 1789 or something?
Exactly. Above a certain level of seniority it's a ritual for the officials to submit letters of resignation after
every Presidential election, including those where the incumbent won. The newly elected President then has the flexibility to choose people (s)he knows will carry out their policies. But because Trump did it and G. W. Bush did it, it was sinister and possibly illegal, while when Clinton and Obama did it that was normal.
What the appropriately self-named "Lint Head" ignorantly or dishonestly failed to mention is that Trump's appointments needing Senate confirmation are not lagging for lack of action on Trump's part, but the lag is due to Ds' obstructive slow-walking of the approvals process.